Image quality of image data generated by a digital still camera (DSC), digital video camera (DVC) or the like can be adjusted in a desired manner using an image retouching application run on a personal computer. An image retouching application typically has an image quality adjusting function for automatically adjusting image quality of image data; using this image quality adjusting function, image quality of an image output from an output device can be improved. CRTs, LCDs, printers, projectors, and television receivers, for example, are known image output devices.
A printer driver, which controls the operation of a printer as an output device, also has a function for automatically adjusting image quality, and the quality of printed images can be improved using such a printer driver as well.
One important factor determining image quality of print data is color balance. Color balance of image data is strongly affected by the light source used when the image data was generated. Light sources include natural light sources such as sunlight, artificial light sources such as fluorescent and incandescent lighting, depending on the shooting location or time or shooting, or selected according to user preference. Additionally, the spectral distribution of light differs depending on the type of light source. Thus, for a given subject, images having shifted color balance (color cast) may occur under light sources of different types. For example, where a light source that contains strong blue light (such as fluorescent lighting) is used, images may have a bluish cast. Adjustment for such shift in color is termed “white balance”. Where there is a significant color shift, a shift in color balance will be noticeable as well. Thus, there is employed a method of carrying out adjustment of white balance in such a way as to minimize color shift in image data, in order to improve image quality (see, for example, JP10-271524A and JP2000-299801A).
White balance adjustment is executed in such a way as to minimize color cast in image data across the board. However, in some instances color cast in image data can vary in a number of ways, depending on color of a certain subject, for example.
Thus, there were some instances in which image quality may not be improved sufficiently despite carrying out white balance adjustment in the conventional manner. Such problems are not limited to images created by DSCs, but are common to images created by DVCs and other such image generating devices as well.
With the foregoing in view, it is an object of the present invention to provide appropriate automatic adjustment of image quality depending on shift in color of the light source.